Avocados to blame in mysterious Duke primate deaths

The Duke Lemur Center has zeroed in on avocados as the cause of death for four aye-ayes in October.

Officials said a natural toxin found in avocados caused damage to the heart muscles of the primates, resulting in their deaths. Four aye-ayes died within 36 hours on Oct. 25 and 26. A fifth animal also became sick, but has recovered.

Avocado leaves, pits, skin and possibly the fruit contain a toxin called persin that the plant produces as a natural antifungal. Persin is not harmful to humans, but it is known to be an issue for domestic cattle, horses and goats, as well as several species of bird. Veterinarians said avocado toxicity occurs randomly in animals and hasn’t been studied much.

Captive lemurs at Duke and elsewhere had been fed avocados routinely, and the green fruit had been a favorite of the Duke lemurs, officials said. But it’s unclear just why the aye-ayes succumbed in quick succession in late October. On Oct. 24, all 13 of the center’s aye-ayes had eaten avocados from the same box, but only five got sick.

Lemur Center Operations Director Greg Dye said avocado will no longer be served to Duke’s 230 rare and endangered animals, and the center’s veterinarians have communicated with colleagues around the world, warning them to stop feeding avocados to the primates.

The conclusion to the medical mystery was reached after an extensive investigation that included testing the air and water at the center for bacteria and pathogens. The Centers for Disease Control in Atlanta and a lab at Michigan State University analyzed tissue samples and stomach contents of the animals. All four of the dead aye-ayes had fluid around their hearts. The cause of death was ruled “acute cardiac toxicity.”

The animals could not be saved by center staff, who tried IV fluids, oxygen, breathing tubes and cardiac resuscitation when they saw the aye-ayes in distress.

Being nocturnal, most lemurs in Duke’s aye-aye colony were named for horror characters. Those who died were Morticia, nearly 28, the mother of seven aye-ayes bred at the Lemur Center; Norman Bates, 7, Morticia’s son; Merlin, 22, who spent six years on loan at the San Francisco Zoo; and Angelique, 11, who made news in 2005 for being the first aye-aye born to parents also born in captivity.

Grendel, 6, is eating and behaving normally now, after resting and slowly regaining his strength.